1. Field of the Invention
The invention relates to an illumination device and, more particularly, to a rotatable illumination device.
2. Description of the Prior Art
So far illumination devices equipped with light bulbs can be divided into two types including direct light type and side light type. In side light type illumination device, a conventional E27 bulb or a light emitting diode bulb has to be equipped with a reflective cover for guiding light. However, the light emitting efficiency of the conventional side light type illumination device is about 50% to 70% since the reflective cover causes light loss. Therefore, the light emitting side of the light bulb in some side light type illumination devices is directed to a specific direction so as to increase the light emitting efficiency. However, after installing the illumination device on a lamp holder, the light emitting side of the light bulb usually cannot be kept in the correct direction so that the light emitting efficiency is reduced. Thus, how to rotate the illumination device to an appropriate light emitting angle after installing the illumination device on the lamp holder becomes a significant design issue.